Thermostatic air circulation fan control for combustion heaters



Apnl 11, 1950 w. D. HALL 2,503,262

THERMOSTATIC AIR CIRCULATION FAN con'moz. FOR comsusnon HEATERS Filed Dec. 12, 1947 AAMQ A2.

Patented Apr. 11, 1950 UNITED STATES PATENT OFFICE THERMOSTATIC AIR CIRCULATION FAN CONTROL FOR COMBUSTION HEATERS 'Wllllam D. Hall, Elkins, W. Va.

Application December 12, 1947, Serial No. 791,177

Claims. 1

This invention relates to heating systems and more particularly to such systems that have a circulating fan or pump for circulating the heating medium. This application is a continuation in part of my prior copending application Serial No. 347,951, filed July 27, 1940, entitled Control systems, which-application is now abandoned, and also a continuation in part of my prior copending application Serial No. 735,983, filed March 20, 1947, entitled Control system for heaters. The present invention is an improvement on a, portion of the system of those applications when that portion is applied to certain types of small heaters.

The invention hereinafter to be fully described has for its primary object the provision of means for delaying the starting of the circulating fan of a hot air or hot water system until such time as the heater is warm. While the broad idea of starting the flow of circulating air only after the heater has become warm is not new, my invention resides in radically new and different means for accomplishing this end. Another and more detailed object of my invention resides in the provision of means for driving a fuel pump of a heater by the same motor as drives the fan and still delay the starting of the fan until the heater becomes warm.

My invention employs a motor mounted between the fan and the pump. The fan is loosely carried by its shaft so that it does not revolve at normal speed when the motor is started. However, when the heater becomes warm, a thermal element deflects and causes positive engagement between the fan and shaft thereby causing the fan to rotate at normal speed. In the description, I am setting forth the details of my invention and the best mode of applying it, but it is understood that the scope of my invention is being set forth in the claims.

In the drawings:

Figure 1 is a schematic diagram of the invention, except for the portion whichshows the thermal clutch for the fan and this portion is shown in section.

Figure 2 is a sectional view taken along line 22 of Figure l.

Figure 3 is a schematic diagram of a modified form of the invention, except that the portion which shows the thermal clutch for the fan is shown in section.

Referring to Figure 1, a main driving motor III has shafts H and I2 projecting therefrom in opposite directions, which shafts respectively drive fan l3 and fuel pump It. The fuel pump I4 is a l chamber |9 and leaves through radiator from turn starts pump l4.

whence it then passes to the exhaust pump II. The fan I3 is adapted to propel air toward the left, and is mounted on a hub 2| which hub has a center hole larger than shaft ll, whereby the hub 2| is free to move independently of shaft The shaft H has collars 22 and 23 mounted on opposite sides of th hub 2|. The bimetallic strip 24 of U-shape has its right end rigidly attached to the hub 2| and has its left end slitted so that it passes by shaft ll without touching the latter.

The operation of the system of Figure 1 is characterized by starting motor l0 which in flow into combustion chamber, but due to delays heat is not immediately generated in radiator 20.

the igniter as well as the usual delay in any heater in coming up to working temperature. Before the heater radiator 20 becomes warm the fan I3 is not rotated very fast inasmuch as it is only loosely mounted on shaft I. Considerable torque is required to rotate fan l3 at high speed and the loose fit of hub 2| on shaft II is insufficient to provide that torque. However, as the heater becomes warm, the bimetallic strip 24 begins to expand and uncoil, whereby the ends of this strip move away from each other. When the heater is heating, the fan is rotating slowly and this moves som heat from the radiator 20 to the bimetallic strip 24. As soon as the heater radiator 20 is warm, the bimetallic strip 24 will have sufliciently expanded to force hub 2| into positive contact with collar 23, hence, the fan Referring to Figure 3, the motor It drives the combustion air pump 30 and the liquid pump 3| (which feeds oil into the combustion chamber I! through pipe 33). The oil is mixed with air The fuel then begins to which flows through pipe 32. The left end of shaft H has a tapered portion 25 whereby the left end is larger than the remainder of the shaft. The hole in hub 2| is similarly tapered. In this device the fan l3 tends to propel air to the left, and hence when the fan is running at high speed the air leaving the fan exerts a force on the fan It tending to move hub 2! to the right. Therefore, the fan l3 will not attain substantial speed prior to a more positive engagement. When the radiator 20 becomes warm, bimetallic strip 24 uncoils and forces the hub into contact with portion 25 of the shaft. As the heater increases in temperature, the engagement of hub 2| and shaft 25 improves whereby the fan accelerates gradually to normal speed.

I have referred to exhaust pump ll as a fuel pump, even though it is supplemented by a separate pump l5 (which may not even be rotated as a unit with pump it) and even though pump l5 provides all of the force for moving the liquid fuel to the combustion chamber I9. This is true inasmuch as in a broad sense the pump It is necessary in order to deliver a combustible mixture to the chamber l9. Such a mixture is in the true sense "fuel and the pump it is necessary in order to supply the combustion air thereof. In Figure 3, the motor drives air pump 30 and oil pump 3|, either or both of which are, broadly speaking, a fuel pump.

In applicant's copending application S. N. 735,983 hereinbefore mentioned the broader aspects of the invention herein described and claimed are shown. That copending application illustrates one form of invention, in Figures 1, 2 and 5 wherein the fan and motor are on separate shafts and connected by a thermal clutch which responds to heater temperature. In Figure 8 of the copending application I illustrated a heater fan and motor on separate shafts connected by an electromagnetic clutch controlled by a thermal element that was responsive to heater temperature. While the broad aspects of these systems arethe same and are herein claimed, it is emphasized that the present application discloses a single shaft for both the motor and fan, and the present system is far less expensive and compact than my earlier system. It is therefore ideally suited for small heaters.

I claim to have invented:

1. In a heating system, a heater, a fan for dissipating heat from the heater, 2. motor, thermostatic coupling means for automatically operatively coupling the fan to said motor when the heater is heated and uncoupling the fan from the motor when the heater is cooling, and a pump driven by said motor for effecting fuel fiow to said heater.

2. In a heating system, a combustion heater, an exhaust pump for removing products of combustion from said heater, a fan for circulating air over said heater, a common motor for driving said pump and said fan, and thermostatic coupling means between the fan and motor for un coupling the motor from the fan when the heater is cool and coupling the motor and fan when the heater is hot.

3. In a heating system, a combustion heater, 0. pump for effecting flow of combustion air into the heater, a fan for circulating air to be heated over the heater, a common motor for driving the pump and fan. and a, thermal clutch interposed between the fan and motor for connecting the two together without slippage when the heater is hot and for permitting slippage between them when the heater is cool, said thermal clutch including a thermal element subi ect to heat from the heater for controlling the thermal clutch.

4. The system defined by claim 1 in which the fuel pump is an exhaust pump adapted to exhaust the products of combustion and to cause combustion air to flow into the heater.

5. The system defined by claim 1 in which the fuel pump causes oil to flow into the heater.

6. The system defined by claim 1 in which the said fuel pump is an exhaust pump to draw in combustion air and to exhaust the products of combustion; and a separate fuel pump for causing oil to flow to the heater and being substantially the sole force for causing such oil to flow.

7. The heating system defined in claim 1 in which said motor has a shaft, in which the fan has a hub loosely mounted on the shaft, and in which the thermostatic coupling means effects a positive driving connection between the shaft and said hub in response to heat.

8. The heating system defined by claim 1; in which the thermostatic coupling means comprises: a hub carrying the fan, said hub defining a tapered axial hole therein, a shaft driven by the motor and tapered parallel to the walls of said hole, and a thermal element which when heated forces said tapered portions together; said motor including means to rotate the same in such direction as to tend to cause the fan to exert a force on the hub tending to cause said tapered portions to move away from each other.

9. The heating system of claim 8 in which the thermal element is located in the path of heated fluid from the heater and on the downstream side of said heater.

10. In a heating system, a combustion heater, a fan for dissipating heat from the heater, a motor, a thermal control element located in the path of heated fluid set up by said fan and on the downstream side of said heater, means operated by said thermal control element for controlling the degree of coupling between the motor and the fan to cause the fan to run at a speed substantially less than that of the motor when the element is cool and at motor speed when the element is hot, said means including means for providing sufilcient coupling between the motor and fan when said element is cool to rotate the fan at suflicient speed as to move some heat from the heater to said element, and means driven by said motor for delivering fuel to said heater.

WILLIAM D. HALL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,233,518 Snyder July 17, 1917 1,684,599 Ryder Sept. 18, 1928 1,749,499 Modine Mar. 4, 1930 1,919,743 Peters July 25, 1933 2,172,667 Nelson Sept. 12, 1939 2,243,609 Spackman May 27, 1941 2,295,841 Hallinan Sept. 15, 1942 2,308,507 Hallinan Jan. 19, 1943 2,381,567 Y Bonham Aug. 7, 1945 2,437,287 Woods Mar. 9, 1948 

